1. Field of the Invention
This invention relates in general to door locks. In particular, the invention relates to keyless door locks that can be operated only from the secured side of the door.
2. Description of the Related Art
Dead bolt locks have been used on entrances to homes, hotels and apartments for many years. Typically, these locks use a key and tumbler system that allows them to be locked and unlocked from outside. This leaves the effectiveness of the lock dependent on the integrity of personnel having pass keys to the entire complex. For their own peace of mind, many apartment dwellers and guests at hotels would prefer a lock that can only be unlocked from inside the room.
Several types of keyless locks are sold, but they have drawbacks. A common type uses a cylindrical bolt with a groove ring that slides into a slot that is affixed to the door; the bolt is secured to the door frame with a chain. This type of lock is often difficult to secure and unlock, and some versions can be defeated by forcing the door open. Also, most versions of this type of lock allow the door to be opened sufficiently to permit cutting the chain from outside the door.